Co-catalytic effect of sewage sludge-derived char as the support of Fenton-like catalyst

Sewage sludge-derived char was successfully employed as the support of heterogeneous Fenton-like catalyst for the first time. Physicochemical properties of the prepared sewage sludge-derived char supported iron oxide catalyst (FeSC) have been evaluated by XRD, SEM, EDS and N2-adsorption/desorption analysis. FeSC exhibited better performance in discoloration of AOII than wood sawdust-based carbon supported iron oxide catalyst (FeWC) both in batch experiment and continuous tests. The high inorganic components content of sewage sludge was concluded to have strong correlations with the high catalytic activity of FeSC. To further interpret the co-catalytic effect of inorganic components in sewage sludge, the inorganic components were removed from the sewage sludge and then a series of catalysts were prepared by the addition of iron, as well as silica and/or alumina to the sewage sludge free of the inorganic components. It was found that the removal of inorganic fraction remarkably decreased the catalytic activity of iron-containing catalyst. The insertion of SiO2 favors the increase in catalytic activity due to the formation of both hydrogen bonds between H2O2 and siloxane bridges and the acidic microenvironment near the surface of silica phase. While the addition of Al2O3 in sewage sludge as basic sites can facilitate the degradation of H2O2, and the characteristic of Lewis acidity of alumina can accelerate the reduction of Fe3+ to Fe2+ by H2O2.

► Sewage sludge was employed as support of Fenton-like catalyst for the first time.
► Inorganic components in FeSC showed strong co-catalytic effects in Fenton-like reaction.
► Co-catalytic mechanism of two main inorganic components, SiO2 and Al2O3, was investigated.